The U.S. Preventive Services Task Force (USPSTF) has issued a Grade B recommendation for annual low-dose CT screening for individuals between the ages of 50 and 80 who are at high risk for lung cancer.
The recommendation, published in the July 30 issue of Annals of Internal Medicine, gave high weight to the National Lung Screening Trial (NLST), which was halted in November 2011 after an interim analysis linked annual CT screening with a 20 percent reduction in lung cancer mortality. The trial indicated a number needed to screen to prevent one lung cancer death of 320 participants.
The task force also considered three other trials focused on CT screening: the Danish Lung Screening Trial (DLSCT), which showed a relative risk of 1.37 of lung cancer mortality in the CT group after a median follow-up of 4.8 years; the Detection and Screening of Early Lung Cancer by Novel Imaging Technology and Molecular Essays (DANTE), which indicated a relative risk of lung cancer mortality of 0.83 among the CT-screened group after a median follow-up of 34 months; and the Multicentric Italian Lung Detection (MILD) study, which found a relative risk for lung cancer mortality of 1.0 in a biennial CT group compared with a control group.
The USPSTF referred to harms associated with screening, which include false-negative and false-positive results, incidental findings, overdiagnosis and radiation exposure. False-positive findings typically require noninvasive follow up; imaging and clinical follow up were most often performed for individuals with benign disease. Invasive follow up was most often performed in individuals with malignant disease. Incidental findings were reported on 7.5 percent of all CT exams in the NLST.
The magnitude of overdiagnosis is uncertain, but autopsy studies suggest low rates. In the systemic review, Linda L. Humphrey, MD, MPH, of Oregon Health & Science University Evidence-based Practice Center in Portland, and colleagues noted that biomarkers may play a key role in curbing overdiagnosis. “In the future, biomarkers and CT variables, such as volume-doubling time and nodule size, may help discriminate among biologically aggressive and indolent tumors.”
The USPSTF recommended clinicians proceed with caution in recommending screening for patients with significant comorbidity, particularly those who are toward the upper end of the screening age range. It also noted that the trials were conducted in large academic medical centers with expertise in diagnosing and managing abnormal lung lesions.
“Clinical settings that have high rates of diagnostic accuracy using LDCT, appropriate follow-up protocols for positive results, and clear criteria for performing invasive procedures are more likely to duplicate the results found in trials. Implementing lung cancer screening in community settings with similar expertise would increase the odds of achieving maximum benefits while minimizing harms.”
In weighing the benefits and harms, the USPSTF wrote, “Modeling evidence suggests an annual screening program starting at age 55 years and ending at age 80 years (among current or former smokers with a 30 pack-year smoking history and <15 years since quitting) resulted in approximately 50% of lung cancer cases detected at an early stage.” This translates into a 14 percent reduction in lung cancer mortality.
Meanwhile, “The harms associated with this screening protocol are an estimated overdiagnosis of 4% and radiation-induced lung cancer deaths of less than 1%.”
The Medical Imaging & Technology Alliance commended the USPSTF for its recommendation and urged the Centers for Medicare & Medicare Services to expand Medicare coverage for this service for those at risk.